Toner compositions are used with electrostatographic, electrophotographic or xerographic print or copy devices. In such devices, an imaging member or plate comprising a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging the surface of the photoconductive insulating layer. The plate is then exposed to a pattern of activating electromagnetic radiation, for example, light, which selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. The electrostatic latent image may then be developed to form a visible image by depositing firmly divided electroscopic toner particles, for example from a developer composition, on the surface of the photoconductive insulating layer. The resulting visible toner image can be transferred to a suitable receiving substrate such as paper.
Xerox uses two manufacturing strategies in production of its toner parent particle products, a chemical toner process (known as EA or “Emulsion-Aggregation” technology) as well as a conventional production process. Rounded toner particles are produced primarily through the EA chemical toner process.
In the EA chemical toner process, raw materials are dispersed in a solution using water, surfactant, and high-intensity homogenization equipment. This EA chemical toner process is water-intensive and time-consuming. A chemical aggregation process is used to grow the toner particles to a targeted sized. These toner particles are then rounded in a batch process known as coalescence. In the coalescence process, a batch of chemical slurry is mixed and heated in a vessel or reactor to a temperature that is greater than the glass transition temperature (Tg) of the latex resin. The goal of this process is obtain a round particle. A round particle has a shape factor of between 0.97 and 1.0, which varies by product.
As for the conventional toner particle production, this conventional toner technology produces irregularly-shaped toner particles via a process of extrusion and physical grinding. In this process, extruder material is physically ground and classified to achieve the desired particle size and distribution. Other toner particle producers have explored methods to surface-modify conventionally produced toner particles via special grinding and blending processes. Xerox has investigated the feasibility of using equipment, e.g., Hosokawa Cyclomix, to round such conventional particles. In this process using the Hosokawa Cyclomix, the equipment employs additives, heat, mechanical shearing, and agitation to attempt to make round particles. This is very time intensive, not efficient and it requires a lot of energy. The process of modifying conventionally produced toner particles to make round particles takes, for example, multiple hours and normally more than three hours. In addition, the process of modifying conventionally produced toner particles to make round particles may damage an internal structure of the conventionally produced toner particles.
It would be desirable to provide a conventional toner particle process that allows for the production of round particles that is more efficient, takes much less time, results in a consistent toner product, does not impact the internal structure of the conventional toner particle, and enables reduced energy consumption.
Similarly, xerographic toners for Magnetic Ink Character Recognition (MICR) require a certain magnetic remanence and coercivity to allow check scanners (or MICR readers) to read the magnetically encoded text. These toners are normally achieved by doping magnetite (e.g., iron oxide) in to the toner particles. The magnetite is typically acicular and has relatively large dimensions ranging from 0.1 microns to 0.6 microns. A large loading (30 to 50 percent) of these particles is required to achieve the required magnetite's low retentivity. Xerox currently produces MICR particles through the conventional “Banbury” process or utilizing extrusion technology. Then, energy intensive processes like pulverizing and classification are employed to break the particles down to a needed size. However, these energy intensive processes lead to high costs. For example, the current magnetic toners are made normally through a conventional route, where the magnetite is blended with resin and wax and either extruded or made via the Banbury method, which involves large slabs of the mixture being broken down mechanically.
There has been a desired to make a magnetic EA toner for a number of years. EA MICR toners are desired because the process is water based and more environmentally friendly than the conventional process with less excessive heating. All of this leads to lower toner costs.
One of the main EA properties that is desired in an MICR toner particle is to create MICR particles with high circularities. This has been proven difficult to achieve via the conventional toner process. The reason is because the large particle size of the acicular magnetite (i.e., 0.1 to 0.6 micron) makes it very difficult for incorporation into the latex (which has a particle size of around 0.2 microns). This leads to challenges into incorporating magnetite into EA particles and successfully undergoing aggregation and then coalescence. The larger magnetite particle size can provide better tribo and image density. The higher magnetite readings also help with readability of the MICR toner. However, the large magnetite size, loading requirement, and high density makes these type of particles difficult to disperse and stabilize. Thus, incorporation into EA toners is difficult.
Further, magnetite loading and circularity are normally inversely proportional. The high magnetite leverl may lower the amount of latex available for particle formation, and getting enough resin to the surface to spheroidize the particles is one of the primary concerns. Achieving the spheroid shape improves machine performance for EA toners. Another issue is that the required magnetite loadings can cause unacceptable particle morphologies and rough surface structures, which negatively impact toner additive blending.